The present invention relates to a system for dressing or blueprinting a centrifugal clutch to match the drum and shoes for better performance.
A typical centrifugal clutch has a drive shaft, rotatable by a power source, on which clutch shoes are mounted, and a driven shaft on which a hollow drum is mounted. The drive shaft of the clutch may be the crankshaft of a motor. The clutch shoes are mounted so that they rotate with the drive shaft, but can move outwards into frictional engagement with the inside of the drum when the drive shaft rotates. The frictional engagement transmits rotational motion and torque from the drive shaft to the driven shaft.
In order to provide the best consistent performance (such as torque transfer) for a centrifugal clutch, it is important to match the shoes to the drum. In one current method, a machinist mounts the clutch (without the drum) in a lathe with the shoes spaced out to the engaged position. The lathe is turned on at a slow speed so that the outside of the shoes can be machined to a desired diameter. The drawback with this method is that, since the drum is not in place the clutch has to be rotated at a slow rate so that the shoes do not fly oil the clutch. This, of course, means a slow dressing process. Also, since the shoes are not under load, they do not rotate to the same position that they normally would be in if they were subjected to a torque load. Some clutches are designed such that the shoes rotate several degrees when under load.
Another method to dress the shoes is to leave the shoes on the hub and hold a piece of emery paper to the outside of the shoe and sand the shoes. This method also has drawbacks since there is no way to make sure the shoes are sanded to the correct radius that is needed to match to the drum. Also, it is not possible to replicate the offset that occurs during loading.
In order to dress a drum and remove high spots, one current method is for the person servicing the drum to hold sandpaper in their hand and sand the inside radius. The obvious problem is that there is no way to make sure that the material is removed in a consistent manner. Another method is to use a drill and a small abrasive sanding roll. The roll is pressed against the drum as the person servicing the drum works their way around the inside of the drum. This produces inconsistent results since variations in the pressure and speed as the person sands results in the removal of different amounts of material.
A need, therefore, exists for improved products and methods for dressing the drum and shoes in a centrifugal clutch.